Biochar And Marble Waste: A Great Match For Sustainable Solutions In Almería, Spain

Biochar

An effective way to sequester carbon and store it for hundreds of years is through the use of biochar, a carbon-rich product that was used thousands of years ago by the indigenous tribes of the Amazon rainforest. Any type of biomass rich in organic matter can be utilized to make biochar - plants, animal excreta, organic waste, crop remnants.  Unlike traditional charcoal, biochar is “burned” or “baked” anaerobically (without oxygen) through the process of pyrolysis, under the ground, in modern kilns, or in efficient pyrolysis facilities. 

Why would anyone go through the effort to make biochar and what are its uses to the ecosystem or human health? The answer is that biochar sequesters carbon, a critical activity in mitigating  climate change.  It can also improve agricultural yields, enrich soil health, and protect water sources with its high water-holding capacity.  These are all essential components of long-term, sustainable agricultural practices, meaning that biochar could be a far more sustainable solution than any other solution out there. Because of this, crop burning which is sometimes used by farmers around the world, could be substituted with a more innovative and eco-friendly option. Industrial agriculture can also benefit from this miraculous commodity as well, since biochar has the ability to retain  moisture in the soil, leaving a reservoir of water for a plant to tap into in times of drought. This approach is economically profitable since it saves water, stimulates agricultural productivity and sequesters carbon.

Marble Sludge

An additional resource that can be applied in agriculture is derived from the marble industry’s waste material--the less popular, yet promising , marble sludge. Since the 1500's, residents in Southern Spain have freely collected marble from the mountains. Today, Macael, a municipality in Almería, is the predominant epicenter of the famous ornamental rock industry with the company Cosentino being headquartered there. Modern collection includes a variety of marble, ranging from White Macael Río to Marmol Verde (Green Marble). For Almería, marble signifies economic prosperity, so it has long been a crucial industry to the region.  Marble sludge, consisting mainly of Calcium Carbonate (98%), is the industry’s by-product obtained from the manufacturing and processing process, specifically after cutting and polishing. The marble industry generates enormous amounts of waste every year, which is stored in marble mud rafts near the mining farms. Incorrect management of this waste can lead to environmental problems, including air and water contamination from to dust release, causing respiratory harm. However, as the Ibero-American Agency for the Diffusion of Science and Technology revealed in a 2018 study, contaminated soils were cleaned using the residues of the marble industry, which also improved plant growth. 

Mud raft in Almería. Image Source: F. Discover  Logran regenerar suelos contaminados y recuperar su vegetación . [accessed 2020 October 27]. http://www.dicyt.com/viewNews.php?newsId=37279

Water Concerns

Almería is one of the driest areas in Europe, and the water source for the greenhouses comes from groundwater. According to a 2019 study published in the Spanish Journal of Soil Health, Almeria’s vast greenhouses require very large amounts of clean water. This demand has not only led to notably lower water table levels, but also to unhealthy water quality, calling for multiple sustainable solutions from the combined work of policy-makers, scientists, and educators, and changes in irrigation consumption. The study drew attention to addressing both soil health and water quality through the adoption of marble sludge and biochar paired together, which would improve water retention in the soil, leading to a reduced demand for virgin water use from the aquifers. 

Char-sludge Mix

The 2019 study used marble residues in the form of the mud from the waste rafts through the Macael Stone Technology Center and mixed with biochar. Although larger scale studies still need to be conducted, the results of the experiment did show that a marble sludge and biochar mix improved the soil’s retention of water, taking into account the local Mediterranean climate of southern Spain. Moreover, other studies have shown both biochar and marble sludge as being well suited to cleaning heavy metal contamination in soils. The waste from the greenhouses is a valuable source of biomass that can be made into biochar, and utilizing such recycled material would create a circular flow with little need to purchase raw biochar.

On a final note, even though agricultural waste is not currently managed perfectly, we have a great opportunity to begin doing better. It is clear that agricultural waste, when turned into biochar, is able to provide valuable contributions to sustainable regenerative agriculture, yielding higher produce, stimulating a circular economy, and sequestering carbon. Along with the biochar, the waste from the ornamental rock industry in Almería may positively affect the soil’s ability to retain water and help it become free from heavy metal contamination, leading to a positive change in soil health, reduced water usage and increased crop yields. Together, these materials provide a promising pathway towards sustainable agriculture in the Almeria region and should be considered for future use in the fight against climate change. 

~Contact Amata Green to find out about our sustainability projects in Almeria, Spain!  

About the author:  Ms. Olga Cheltsova is a Sustainability Intern at Amata Green, and is a graduate student in Environmental Science and Policy at George Mason University.  She has a particular interest in renewable energy, regenerative agriculture, permaculture methods, and sustainable practices as tools to address planetary and human health. 

Edits by Natalie Kra and Sandia Martin

Bibliography:

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2. Ramesh, S., Here, P., -, K., -, H., & -, S. (2019, September 26). Biochar could be the solution to crop burning that Indian farmers were waiting for. Retrieved October 08, 2020, from https://theprint.in/science/biochar-could-be-the-solution-to-crop-burning-that-indian-farmers-were-waiting-for/296494/

3. Ajayi, A.E., Holthusen, D., Horn, R., 2016. Changes in microstructural behaviour and hydraulic functions of biochar amended soils. Soil and Tillage Research 155, 166–175. https://doi.org/10.1016/j.still.2015.08.007

4. The Marble of Macael - Turismo Almanzora. [accessed 2020 October 27]. https://turismoalmanzora.com/en/towns/tourism-macael/the-marble-of-macael-2/

5. Cobo-Ceacero, C.J., Cotes-Palomino, M.T., Martínez-García, C., Moreno-Maroto, J.M., Uceda-Rodríguez, M., 2019. Use of marble sludge waste in the manufacture of eco-friendly materials: applying the principles of the Circular Economy. Environ Sci Pollut Res 26, 35399–35410. https://doi.org/10.1007/s11356-019-05098-x

6. Salinas, J., García, I., del Moral, F., Simón, M., 2018. Use of marble sludge and biochar to improve soil water retention capacity. Revista SJSS 2018, V8. N1. 08. https://doi.org/10.3232/SJSS.2018.V8.N1.08

7. González, V., Salinas, J., García, I., del Moral, F., Simón, M., 2017. Using marble sludge and phytoextraction to remediate metal(loid) polluted soils. Journal of Geochemical Exploration, Remediation of Polluted Soils - Part 1 174, 29–34. https://doi.org/10.1016/j.gexplo.2016.03.008

Photo credit: Edward Burtynsky (Almeria Spain greenhouses)